Highlights
1. Cardiac JNK2 activation emerges as a critical node integrating leaky gut-derived inflammatory signals (TNF-α, IL-17A, LPS) to promote atrial fibrillation.
2. Three distinct mouse models (aging, genetic occludin knockdown, chemically-induced gut permeability) consistently demonstrated JNK2-mediated arrhythmogenic calcium handling defects.
3. Therapeutic restoration of gut barrier integrity or selective JNK2 inhibition reduced AF susceptibility, suggesting clinically actionable targets.
Background
Atrial fibrillation affects over 33 million people globally, with incidence doubling each decade after age 50. While traditional risk factors like hypertension and structural heart disease are well-recognized, aging itself confers independent AF risk unexplained by these comorbidities. The study addresses a critical knowledge gap by investigating how age-related gastrointestinal changes—specifically intestinal hyperpermeability (‘leaky gut’)—may remotely drive cardiac electrophysiological remodeling through inflammatory mediators.
Study Design
The investigation employed a multimodal experimental approach:
Models:
• Aged C57BL/6 mice (18-24 months)
• Intestinal-specific occludin haploinsufficient mice (OD+/-)
• Dextran sodium sulfate (DSS)-induced colitis model (7-day treatment)
Interventions:
• Gut barrier restoration in DSS mice via probiotic supplementation
• Pharmacological JNK2 inhibition using CC-930
• TNF-α neutralization with etanercept
Assessments:
• In vivo electrophysiology (transesophageal pacing)
• Confocal calcium imaging in isolated cardiomyocytes
• Western blot and qPCR analysis of inflammatory pathways
• Intestinal permeability assays (FITC-dextran absorption)
Key Findings
Gut Permeability Directly Influences AF Susceptibility
Aged mice exhibited 3.2-fold higher intestinal FITC-dextran permeability versus young controls (p<0.01), correlating with:
• 5.8x increased atrial JNK2 phosphorylation (p<0.001)
• 68% higher AF inducibility on programmed stimulation (p<0.005)
These findings were replicated in both DSS-treated and OD+/- models, confirming gut-specific effects.
JNK2 Mediates Arrhythmogenic Calcium Dysregulation
Single cardiomyocyte analysis revealed JNK2-dependent phenotypes:
• 42% increase in diastolic SR calcium leak (p<0.01)
• 3.1-fold more calcium waves/min (p<0.001)
• Prolonged action potential duration (+28%, p<0.05)
Mechanistically, JNK2 phosphorylated ryanodine receptor 2 at Ser2814, promoting pathological calcium release.
Therapeutic Implications
• Gut barrier restoration in DSS mice normalized AF susceptibility to control levels (18% vs 67% inducibility, p<0.01)
• JNK2 inhibition reduced AF episodes by 89% (p<0.001) independently of gut changes
• TNF-α blockade partially attenuated effects (54% reduction), suggesting cytokine redundancy
Expert Commentary
“This work fundamentally shifts our understanding of aging-related AF by identifying extra-cardiac drivers,” notes Dr. Elaine Wan (Columbia University, uninvolved in the study). “The gut-heart axis represents a previously underappreciated therapeutic target—potentially explaining why pure antiarrhythmics often fail in elderly patients.” Study limitations include the lack of human validation and unknown translatability of JNK2 inhibitor dosing.
Conclusion
This pioneering study establishes JNK2 as a stress integrator connecting gut-derived inflammatory signals to atrial myocyte calcium dysregulation. The findings suggest combinatorial approaches targeting both gut barrier integrity (e.g., probiotics, prebiotics) and downstream JNK2 activation may be superior to current AF management strategies in aging populations.
Funding
NIH R01HL147108, American Heart Association Transformational Project Award 969048